The invention relates to an apparatus and method for forming a clay slab. More particularly, the invention is a slab roller and an associated method for working prepared clay into a relatively flat clay slab having a generally uniform thickness of the type used in making clay pottery, sculpture and artwork. In a preferred embodiment, the invention is a slab roller that is oriented in a vertical direction. In another preferred embodiment, the invention is a slab roller configured to draw prepared clay between opposed panels of a flexible material to form a relatively flat clay slab having a generally uniform thickness.
Clay used in making pottery, sculpture and artwork is typically cut from a large block of prepared clay and worked (also referred to as “molded”) into a relatively flat clay slab having a generally uniform thickness. Various equipment and techniques are employed for working the clay depending on the desired size, shape and uniformity of the clay slab. Smaller clay slabs may be formed by hand using a rolling pin on a flat surface, such as a table top or counter, with or without guide rails for controlling the thickness of the clay slab. An example of a known apparatus for forming a clay slab by hand is commercially available under the trade name Activa® Slab Roller and includes a 10.5 inch rolling pin, a rolling board and a plurality of rails for forming clay slabs having various generally uniform thicknesses. Larger clay slabs are typically formed using a manually-operated slab roller machine mounted on a frame. In some instances, the rollers of the slab roller machine may be power-driven, for example by an electrical motor. Commercially available examples of power-driven slab roller machines include the Bailey™ tabletop Minimight™ A Slab Roller, the convertible Brent® SR-14 Slab Roller and the portable Amaco® Mini T-4 Slab Roller.
Regardless, all known slab rollers have the disadvantage that the slab roller is oriented in a horizontal direction so as to work the prepared clay and form the clay slab on a horizontal surface, such as a tabletop, counter or elongated workspace of the slab roller. However, a slab roller oriented in a horizontal direction occupies a substantial amount of floor space, which in most pottery, sculpture and artwork workshops is limited. Although some slab rollers are configured to be moved from a horizontal orientation for working to a vertical orientation for storage, such slab rollers still require a substantial amount of floor space while forming the clay slab and furthermore require an additional expenditure of manpower and time to convert the slab roller from the horizontal orientation to the vertical orientation. A horizontally oriented slab roller also provides no mechanical advantage to the process of molding the prepared clay into a relatively flat clay slab having a generally uniform thickness. In particular, feeding the prepared clay into the slab roller is not assisted by gravity. To the contrary, gravity works against the molding process with a conventional slab roller since the clay slab tends to bunch up as the weight of the prepared clay exiting the rollers experiences increasing friction with the horizontal table.
Another disadvantage of the known slab rollers is that one or more rollers are driven by a complex arrangement of cranks, gears, cables or the like, directly over the prepared clay. The driven rollers operate to apply a pushing force to the prepared clay, similar to a rolling pin, to form the generally planar clay slab. In many instances, a drive board or a panel of flexible material, such as a relatively thin sheet of plastic or canvas, is placed between the roller and the clay, or between the horizontal surface and the clay, to prevent adhesion of the clay to the rollers and the horizontal surface. The roller may also be knurled or provided with a roughened exterior surface so as to grip the sheet of flexible material or drive board in a positive manner. The use of a driven roller to drive the clay often results in the clay slab having an undesirable grain direction and/or an uneven or rough exterior surface. A predetermined grain direction is undesirable because non-isotropic stress patterns can develop in the work piece during firing and subsequent quenching, which may cause the finished piece to shift or warp. A clay slab having an uneven or rough exterior surface can result in the finished piece of clay pottery, sculpture or artwork having an undesirable exterior surface.
Other shortcomings and disadvantages inherent in slab rollers oriented in a horizontal direction include the tendency for complicated gearboxes that transfer force from the crank to the rollers to wear out, fail or require frequent adjustment. In addition, the known slab rollers include inferior adjustment mechanisms for adjusting the distance between the driven rollers, and consequently, the thickness of the clay slab. Adjustment mechanisms for existing slab rollers are not synchronized, and thus, do not always produce a clay slab having a generally uniform thickness. Furthermore, the panels of flexible material (e.g. canvas fabric) utilized with most existing slab rollers are not integrally formed or attached to one another in any manner. Accordingly, the panels must first be located, arranged on the slab roller and aligned, resulting in a significant expenditure of set-up time before the clay slab can be formed. If the driven rollers are not adjusted accurately, or the loose canvas fabric is not positioned properly and carefully aligned, the prepared clay may tend to wander off to one side, thereby requiring the clay slab to be re-formed and resulting in a further expenditure of time.
Accordingly, there exists an unresolved need for an apparatus and method for forming a clay slab that overcomes the disadvantages of known slab rollers and associated methods. More specifically, there exists a need for a slab roller for working prepared clay into a relatively flat clay slab having a generally uniform thickness of the type used in making clay pottery, sculpture and artwork. There exists a particular need for a slab roller that is not oriented in a horizontal direction so as to work prepared clay and form a clay slab on a horizontal surface, such as a tabletop, counter or elongated workspace of the slab roller. There also exists a particular need for a slab roller that does not utilize one or more driven rollers to drive prepared clay between panels of a flexible material, such as a relatively thin sheet of plastic or canvas, to form a clay slab.